RFR: 8224980: FLAG_SET_ERGO silently ignores invalid values [v2]

[Tobias Hartmann]

On Wed, 15 Feb 2023 06:20:02 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> This code is called only by `CompilerConfig::set_compilation_policy_flags()` to scale 15 flags according to `CompileThresholdScaling`. If the user sets `CompileThresholdScaling` to be too high, then some of the calculated values will be capped.
>> 
>> @veresov @TobiHartmann - do you think some warning messages are needed here?
>> 
>> My thinking is that `CompileThresholdScaling` is a somewhat magical knob. If the user really wants to know what's happening, they should add `-XX:+PrintFlagsFinal` and see the effect on all the affected flags.
>
> Okay - whether this should produce warnings is a distinct issue for compiler folk to decide.

I think it's fine to cap the values of the individual thresholds at their maximum without a warning, when `CompileThresholdScaling` is used.

Similar issues were already discussed in https://github.com/openjdk/jdk/pull/8501.

> I suggest to address this issue in a separate RFE.

@tobiasholenstein did you file that separate RFE?

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PR: https://git.openjdk.org/jdk/pull/12549